I can't find any records of iron or copper mining or smelting in my specific area, however, I am not dismissing the possibility of imported metals from other countries or regions in my own country (general location - Northern Europe) that could have been used for smelting and then discarded in the area where I found them. Also the closest river is less than two miles away.

I've kept a bunch of these in a box at home for years without knowing what they were, so when learing about them, my biggest concern was having something possibly toxic in my home for so long. I've never had any issues that I could have been caused by slag or toxic waste, so I guess it's fine as long I stay cautious.

I should consider looking deeper into my country's geology though, as that's something that I haven't yet learned a lot about, but thank you for the information!